The reaction of the preoptic nucleus of Xenopus laevis tadpoles to osmotic stimulation

Summary The development of the preoptic nucleus of Xenopus laevis tadpoles during metamorphosis was studied and the effect of osmotic stimulation on this process investigated. The development of this region was not affected by treatment for one or more days in hypertonic media. It was found that at the end of metamorphosis the neurosecretory cells in the preoptic nucleus are localized in three regions: the rostro-dorsal, the caudo-dorsal and the ventral region. After osmotic stimulation only the neurosecretory cells of the caudo-dorsal region appeared to have reacted, as indicated by their loss of neurosecretory (PIC positive) material. It is concluded that the cells of this region may be involved in the synthesis of the posterior lobe hormones.The author thanks Prof. Dr. J. C. van de Kamer and Dr. F. C. G. van de Veerdonk for their interest and many helpful discussions, Dr. L. Boomgaart and Dr. A. P. van Overbeeke for correcting the English text and Miss C. M. G. van Bemmel for technical assistance.